Suppression of metal contamination by gettering

Starting-material-related defects and line processes are often blamed for high reliability failure rates of gate oxides. Polished wafers are first observed to have higher gate oxide reliability failure rates compared to epitaxial wafers, leading to the initial presumption that this difference in failure rate is attributed to starting material issues. Further investigations revealed that it is not silicon surface imperfections that are the cause of the high gate oxide reliability failures. Instead, results pinpoint metal contamination as the culprit for high reliability failures. However, metal contamination due to processing of epitaxial wafers is suppressed by the gettering effect of oxygen precipitates inside the silicon substrate.